Two lights flash every 15 and 45 seconds respectively.If the two lights flashed together at 3 p.m.,at what time will they flash together next time?

Answer 1

Very simple, since the LCM of 15 and 45 is 45, they will flash in unison every 45 seconds, so add 45 sec to 3 pm or
3:00:45 pm

Answer 2

Why we have done LCM nd not ised HCF for this??

Answer 3

This answer is very very tati